AU2019445992B2

AU2019445992B2 - Electric Work Machine with Cutting Blade

Info

Publication number: AU2019445992B2
Application number: AU2019445992A
Authority: AU
Inventors: Shinya Hiramatsu; Masaki Nonaka; Koichi Ogawa
Original assignee: Kaaz Corp
Current assignee: Kaaz Corp
Priority date: 2019-05-10
Filing date: 2019-05-10
Publication date: 2022-12-01
Anticipated expiration: 2039-05-10
Also published as: KR102677075B1; US20220338412A1; WO2020230208A1; BR112021021023A2; KR20210114526A; AU2019445992A1; CN113473841A; TWI778288B; JP7184400B2; TW202041139A; EP3967124A4; CN113473841B; JPWO2020230208A1; EP3967124A1; EP3967124B1

Abstract

The present invention is provided with: a cutting blade; an electric motor (5) for driving and rotating the cutting blade; a clutch for engaging and disengaging power transmission between the electric motor (5) and the cutting blade; an operation means for operating the clutch; and a control means (30) for controlling the operation of the electric motor (5). The operation means can switch between a clutch disconnection state in which the power from the electric motor (5) is not transmitted to the cutting blade and a clutch connection state in which the power from the electric motor (5) is transmitted to the cutting blade. The control means (30) stops the rotation of the electric motor (5) within a period including the moment of connection of the clutch by stopping energization of the electric motor (5) after release of the clutch disconnection state and restarting the electric motor (5) after a predetermined time after the rotation of the electric motor (5) is stopped.

Description

TITLE OF THE INVENTION ELECTRIC WORK MACHINE WITH CUTTING BLADE TECHNICAL FIELD

[0001] The present invention relates to control for

reducing electric power consumption in an electric work

machine with cutting blade which includes a cutting blade,

in which the cutting blade is driven by an electric motor.

BACKGROUND

[0002] Conventionally, lawn mowers and grass cutters are

used for mowing lawn and grass. Among these work machines,

machines are known which include a cutting blade arranged

in the horizontal direction, in which the cutting blade is

rotated by a driving source, with an engine or an electric

motor being used as the driving source of the cutting

blade. For example, in a walk-behind grass cutter

disclosed in Patent Literature 1, an electric motor 8 is

used as the driving source of front and rear wheels and a

cutting blade that rotates around the axial center thereof

in the vertical direction.

[0003] The aforementioned walk-behind grass cutter

includes a cutting-blade-system power transmission path 50

composed of a transmission shaft 53 connected to an output

shaft 47 of the electric motor 8 via a coupling 52, and a cutting blade clutch 54 that transmits motive power from the transmission shaft 53 to a cutting blade drive shaft 48 in an engageable/disengageable manner (see Fig. 1 of Patent

Literature 1). According to this configuration, when the

cutting blade clutch 54 is engaged during mowing, rotation

of the output shaft 47 of the electric motor 8 is

transmitted to a cutting blade 6 via the cutting blade

clutch 54, and the cutting blade 6 is rotationally driven.

Citation List

Patent Literature

[0004] Patent Literature 1: Japanese Patent Application

Laid-open No. 2014-239660

SUMMARY

[0005] In a case where an electric motor is used as a

driving source, as in the walk-behind grass cutter

described in Patent Literature 1, enabling operation for an

extended period with one charging of the battery is a

problem. In such a case, it is difficult to mount a large

battery in a work machine in which the machine body is

moved while the operator is walking, as in the case of a

walk-behind grass cutter, and consequently there is a need

to reduce electric power consumption in order to enable

operation for an extended period.

[00061 The present invention solves the conventional

problem described above, and an object of the present

invention is to provide an electric work machine with

cutting blade that can enable operation for an extended

period without making the battery a large size.

[0007] To achieve the above object, an electric work

machine with cutting blade of the present invention

includes: a cutting blade; an electric motor that

rotationally drives the cutting blade; a clutch that

engages and disengages transmission of motive power between

the electric motor and the cutting blade; operation means

for operating the clutch; and controller for controlling

operation of the electric motor, wherein: by means of the

operation means, it is possible to switch between a state

in which the clutch is disengaged in which motive power of

the electric motor is not transmitted to the cutting blade

and a state in which the clutch is engaged and motive power

of the electric motor is transmitted to the cutting blade,

and by stopping energization of the electric motor after a

state in which the clutch is disengaged is released, and

restarting the electric motor after a prescribed time

period elapses after stopping the energization, the

controller stops rotation of the electric motor during a

period that includes a moment at which the clutch is

engaged.

[00081 According to the electric work machine with

cutting blade of the present invention, since an abrupt

increase in current at a moment at which the clutch is

engaged can be eliminated and electric power consumption

can be reduced, operation for an extended period can be

enabled without making the battery a large size.

[00091 In the electric work machine with cutting blade

of the present invention, preferably the controller

recognizes release of a state in which the clutch is

disengaged, based on a signal from a sensor that detects

movement of the operation means. According to this

configuration, the release of a state in which the clutch

is disengaged can be reliably recognized using a simple

configuration.

[0010] The advantageous effects of the present invention

are as described above, and since an abrupt increase in

current at a moment at which the clutch is engaged can be

eliminated and electric power consumption can be reduced,

operation for an extended period can be enabled without

making the battery a large size.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is an external perspective view of an

electric work machine with cutting blade according to one

embodiment of the present invention;

Fig. 2 is a perspective view illustrating the inside

of a motor box of the electric work machine with cutting

blade illustrated in Fig. 1;

Fig. 3 is a perspective view illustrating the electric

work machine with cutting blade illustrated in Fig. 1 when

viewed from a handle side;

Fig. 4 is a perspective view illustrating the electric

work machine with cutting blade illustrated in Fig. 1 as

viewed from the underside;

Fig. 5 is a cross-sectional view illustrating the

structure of a clutch arranged inside a housing deck of the

electric work machine with cutting blade illustrated in Fig.

1;

Fig. 6 is an enlarged view of the clutch illustrated

in Fig. 5, and is a cross-sectional view illustrating a

state in which the clutch is disengaged;

Fig. 7 is an enlarged view of the clutch illustrated

in Fig. 5, and is a cross-sectional view illustrating a

state in which the clutch is engaged;

Fig. 8 is a block diagram illustrating control of an

electric motor by controller relating to one embodiment of

the present invention;

Fig. 9 is an external perspective view illustrating

the vicinity of a clutch lever and a clutch operation detection sensor relating to one embodiment of the present invention;

Fig. 10 is a flowchart illustrating a process from

starting operation until ending operation in the electric

work machine with cutting blade relating to one embodiment

of the present invention;

Fig. 11 is a view illustrating waveforms of a current

I and a voltage V of an electric motor with respect to a

Comparative Example; and

Fig. 12 is a view illustrating waveforms of a current

I and a voltage V of an electric motor with respect to an

Example of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] Hereunder, one embodiment of the present

invention will be described with reference to the drawings.

Fig. 1 is an external perspective view of an electric work

machine with cutting blade 1 (hereinafter, referred to

simply as "work machine 1") relating to one embodiment of

the present invention. Fig. 2 is a perspective view

illustrating the inside of a motor box 2. Fig. 3 is a

perspective view of the work machine 1 when viewed from a

handle side. Fig. 4 is a perspective view of the work

machine 1 as viewed from the underside.

[0013] Although in the present embodiment the work

machine 1 is described using an example of a walk-behind

lawn mower, as will be described later, the present

invention relates to control of an electric motor that

rotationally drives a cutting blade via a clutch, and it

suffices that the object for application of this control

has a similar cutting blade rotation mechanism as the work

machine 1, and for example the object for application of

this control may be a riding lawn mower or a grass cutter.

[0014] First, a general outline of the work machine 1

will be described with reference to Fig. 1 to 4. In Fig. 1,

front wheels 3 are attached to the front of the motor box 2,

and rear wheels 4 are attached to the rear. As illustrated

in Fig. 2, an electric motor 5 is mounted inside the motor

box 2. The rear wheels 4 and a cutting blade 9 (see Fig.

4) are rotationally driven by the electric motor 5. In Fig.

1, a battery 6 which is a power source for the electric

motor 5 is mounted at the rear of the motor box 2.

[0015] A housing deck 7 is provided below the motor box

2, and a grass bag 8 is attached to the rear of the housing

deck 7. As illustrated in Fig. 4, the cutting blade 9 is

arranged inside the housing deck 7. As will be described

in detail later, rotation of the electric motor 5 is

transmitted to the cutting blade 9 via a clutch 20 (see Fig.

), whereby the cutting blade 9 rotates. A disk with fins rotates integrally with the rotation of the cutting blade 9, and a flow of air is generated from the housing deck 7 to the grass bag 8. As a result, grass cut by the rotation of the cutting blade 9 is sent to the grass bag 8 through an outlet 19, and thereby collected in the grass bag 8.

[0016] The work machine 1 is a machine that is used by

an operator while walking. In Fig. 1, operating rods 10

are attached to the machine body, and an operation handle

11, a clutch lever 12 (operation means for the clutch), and

a shift lever 13 are attached to an end of the operating

rods 10. Further, a frame 15 is arranged so as to extend

between the pair of operating rods 10, and a display 16

that displays the rotation speed or the like of the

electric motor 5 is fixed to the frame 15. As illustrated

in Fig. 3, a main switch 17 is attached to the display 16,

and the main power source can be turned on by rotating the

main switch 17.

[0017] In Fig. 1, in a state in which the main power

source has been turned on, the electric motor 5 can be

started by sliding the shift lever 13 (in the arrow "a"

direction), and the speed of rotation of the electric motor

can be gradually increased. An operation lever 14 is

attached in the vicinity of the operation handle 11, and by

operation of the operation lever 14 in a state in which the electric motor 5 is rotating, the rear wheels 4 are driven and the work machine 1 moves forward.

[0018] Even if the electric motor 5 is rotating,

rotational driving of the cutting blade 9 is stopped unless

the clutch lever 12 is operated, and when lawn mowing is to

be performed, it is necessary to operate the clutch 20 (see

Fig. 5) using the clutch lever 12 to switch from a state in

which the clutch 20 is disengaged in which motive power of

the electric motor 5 is not transmitted to the cutting

blade 9 to a state in which the clutch 20 is engaged in

which motive power of the electric motor 5 is transmitted

to the cutting blade 9.

[0019] Hereunder, operation of the clutch 20 will be

described while referring to Fig. 5 to Fig. 7. Fig. 5 is a

cross-sectional view illustrating the structure of the

clutch 20 that is arranged inside the housing deck 7. Fig.

6 and Fig. 7 are enlarged views of the clutch 20. Fig. 6

illustrates a state in which the clutch 20 is disengaged,

and Fig. 7 illustrates a state in which the clutch 20 is

engaged.

[0020] As illustrated in Fig. 5, the clutch 20 is

arranged inside the housing deck 7, and a motor shaft 21 of

the electric motor 5 (see Fig. 2) that is arranged on the

upper side of the housing deck 7 is connected to a drive

disk 22. The motor shaft 21 and the drive disk 22 are connected by a key (not illustrated), and the drive disk 22 also rotates integrally with the rotation of the motor shaft 21.

[0021] In Fig. 6, a brake disc support plate 24 is

attached to the motor shaft 21 via an upper-side bearing 23.

An annular brake disc 25 is attached to the brake disc

support plate 24 so as to be movable in the vertical

direction. In this configuration, even if the motor shaft

21 rotates, because the upper-side bearing 23 is interposed

between the motor shaft 21 and the brake disc support plate

24, the brake disc support plate 24 and the brake disc 25

that is integrated with the brake disc support plate 24 do

not rotate.

[0022] The cutting blade 9 is fixed to the lower side of

a blade holder 26, and a lower-side bearing 27 is

interposed between the blade holder 26 and the drive disk

22. A friction plate 28 is connected to the upper side of

the blade holder 26 in a turn-stopping fashion so as to be

vertically slidable, and when the friction plate 28 rotates,

the blade holder 26 and the cutting blade 9 rotate

integrally with the friction plate 28.

[0023] A spring 29 is interposed between the blade

holder 26 and the friction plate 28, and the friction plate

28 slides in the vertical direction as the spring 29

expands and contracts. In the state illustrated in Fig. 6, the friction plate 28 is pressed by the brake disc 25 and caused to slide downward, and the spring 29 is contracted.

Therefore, the friction plate 28 is separated from the

drive disk 22. This state is a state in which the clutch

is disengaged, and even if the drive disk 22 rotates

integrally with rotation of the motor shaft 21, the

rotation of the drive disk 22 is not transmitted to the

friction plate 28, and the cutting blade 9 does not rotate

either.

[0024] In contrast, the state illustrated in Fig. 7 is a

state in which the pressing of the friction plate 28 by the

brake disc 25 has been released, and as a result the spring

29 extends and the friction plate 28 presses the drive disc

22 due to the repulsive force of the spring 29. This state

is a state in which the clutch 20 is engaged, and thus

rotation of the drive disk 22 is transmitted to the

friction plate 28, and the cutting blade 9 rotates to

enable lawn mowing.

[0025] The work machine 1 includes a switching mechanism

(not illustrated) that switches between a state in which

the brake disc 25 is pushed down to the lower side to

disengage the clutch 20 (state in Fig. 6), and a state in

which the disengaged state of the clutch 20 has been

released and the clutch 20 is engaged (state in Fig. 7).

This switching mechanism is operated by operating the

clutch lever 12 (see Fig. 1).

[0026] In Fig. 1, when the clutch lever 12 is tilted to

the front side in a state in which an operation button 18

at the upper portion of the clutch lever 12 is pressed, the

switching mechanism is activated and the state in which the

brake disc 25 is pushed down to the lower side is released,

the friction plate 28 presses the drive disk 22 as

illustrated in Fig. 7, and the clutch 20 enters an engaged

state and the cutting blade 9 rotates. The cutting blade 9

rotates as long as the state in which the operation button

18 is pressed and the clutch lever 12 is tilted to the

front side is maintained, but when the operator's hand

separates from the clutch lever 12, the clutch lever 12

returns to its original state, and the clutch 20 enters a

disengaged state and rotation of the cutting blade 9 stops.

[0027] The work machine 1 has built-in controller 30 (a

computer) for controlling the operation of the electric

motor 5. The control of the electric motor 5 by the

controller 30 is described below. Fig. 8 is a block

diagram illustrating control of the electric motor 5 by the

controller 30, Fig. 9 is an external perspective view

illustrating the vicinity of the clutch lever 12 and a

clutch operation detection sensor 31, and Fig. 10 a flowchart illustrating a process from starting operation until ending operation.

[0028] In Fig. 8, a signal from the clutch operation

detection sensor 31 is input to the controller 30, and the

controller 30 controls the operation of the electric motor

in response to this signal. As illustrated in Fig. 9,

the clutch operation detection sensor 31 is provided below

the clutch lever 12. The clutch operation detection sensor

31 includes a detection button 32, and in the state

illustrated in Fig. 9 (state in which the clutch lever 12

is not operated), the detection button 32 is pressed by a

pressing plate 33 that is fixed to the clutch lever 12.

[0029] In Fig. 9, by pressing the operation button 18

(arrow b direction) and tilting the clutch lever 12 forward

(arrow c direction), the state in which the clutch 20 is

disengaged is released, and the clutch 20 enters an engaged

state from the disengaged state. Since the pressing plate

33 moves in a direction away from the detection button 32

integrally with the movement of the clutch lever 12, the

detection button 32 that had been pressed by the pressing

plate 33 rises upward, and the signal value that is output

from the clutch operation detection sensor 31 changes.

[0030] That is, by setting the positional relationship

between the clutch operation detection sensor 31 and the

pressing plate 33 so that the detection button 32 rises upward when the state in which the clutch 20 is disengaged is released, the signal value of the clutch operation detection sensor 31 when the state changes becomes a signal value indicating that the disengaged state of the clutch 20 has been released, and it is thus possible for the controller 30 to recognize the release of state in which the clutch 20 is disengaged.

[0031] Hereunder, operations from the start of operation

of the work machine 1 to the end of operation thereof are

described while referring to Fig. 10. In Fig. 10, when

starting operation (step 100), the main power source is

turned on (step 101) by rotating the main switch 17 (see

Fig. 3). By sliding the shift lever 13 (see Fig. 1) in

this state, the electric motor 5 is started (step 102), and

the electric motor 5 rotates (step 103). In this state, in

Fig. 1, by operating the operation lever 14, the rear

wheels 4 are driven and the work machine 1 moves forward.

[0032] On the other hand, as long as the clutch lever 12

(see Fig. 1) is not operated, the clutch 20 is in a

disengaged state and the cutting blade 9 does not rotate,

and in order to cause the cutting blade 9 to rotate it is

necessary to release the state in which the clutch 20 is

disengaged by operating the clutch lever 12 to engage the

clutch 20. As described above, in Fig. 8, a signal from

the clutch operation detection sensor 31 is input to the controller 30, and the controller 30 can recognize the release of the disengaged state of the clutch 20. Upon recognizing the release of the state in which the clutch 20 is disengaged (step 105 in Fig. 10), the controller 30 stops the energization of the electric motor 5 (stops the rotational driving) during a period from the time of recognizing the release until a prescribed time period elapses (step 106 in Fig. 10).

[00331 This control is control that stops energization

of the electric motor 5 during a period that includes the

moment at which the clutch 20 is engaged, and it suffices

that the period of stopping energization of the electric

motor 5 includes the moment at which the clutch 20 is

engaged. Although in the present embodiment the rotation

of the electric motor 5 stops during a period from when the

disengaged state of the clutch 20 is released until a

prescribed time period elapses, since a period from release

of the disengaged state of the clutch 20 until the clutch

is engaged is a momentary period, even if the prescribed

time period is a very small time period of about 0.5

seconds, the moment at which the clutch 20 is engaged will

be included in the period in which rotation of the electric

motor 5 is stopped.

[0034] Whilst the prescribed time period for which

rotation of the electric motor 5 is stopped is not particularly limited, for example the prescribed time period is within the range of 0.5 to 1 second. After the prescribed time period elapses, the controller 30 restarts the electric motor 5 (step 107), and the electric motor 5 rotates once more (step 103). In this state, the clutch 20 is in an engaged state, and the cutting blade 9 rotates due to the rotation of the electric motor 5.

[00351 Thereafter, rotation of the electric motor 5

continues even when a state is entered in which the clutch

is disengaged, and when the state in which the clutch 20

is disengaged is released, although rotation of the

electric motor 5 stops for a prescribed time period, after

the prescribed time period elapses the electric motor 5 is

restarted and thus the rotation of the electric motor 5

resumes (step 105 to step 107). When the work is finished,

the main power source is turned off (step 104), and

operation is ended (step 108).

[00361 As a result of repeated experiments conducted by

the inventors of the present application in order to

achieve a reduction in the electric power consumption, the

operation control of the electric motor 5 when the clutch

is operated as described above has been derived based on

the finding that a change in the current at the moment at

which the clutch 20 is engaged is large. Hereunder, the

present invention is described more specifically while referring to measurement results obtained with respect to a

Comparative Example and an Example.

[0037] In the Comparative Example, although the basic

structural configuration of the work machine is the same as

the work machine 1 according to the above embodiment, the

Comparative Example has a configuration so that control

that stops energization of the electric motor 5

(hereinafter, referred to as "energization stopping

control") is not executed during a period from when the

disengaged state of the clutch 20 is released until a

prescribed time period elapses. That is, rotation of the

electric motor 5 continues irrespective of the operation of

the clutch 20. The Example is configured so that

energization stopping control is added to the configuration

of the Comparative Example. With respect to the

Comparative Example and the Example, a voltage measuring

probe and a current measuring probe were connected thereto,

and voltage values and current values were measured

chronologically using a data logger.

[0038] For the Comparative Example and the Example, the

period of one cycle was set to 10 seconds, with an engaged

state of the clutch 20 being set to 9 seconds, and a

disengaged state of the clutch 20 being set to 1 second.

Fig. 11 illustrates waveforms of a current I and a voltage

V of the electric motor 5 with respect to the Comparative

Example. The abscissa axis represents the elapsed time t

(s), and the ordinates axis is used to represent both the

current I (A) and the voltage V (V) (the same applies with

respect to Fig. 12).

[00391 In Fig. 11 that relates to the Comparative

Example, during a period Ti after the start of measurement,

the clutch 20 is in an engaged state and the cutting blade

9 is rotating. During a period T2 (period of 1 second)

that follows the period Ti, the clutch 20 is in a

disengaged state, and although rotation of the electric

motor 5 continues, rotation of the cutting blade 9 is

stopped. In the period T2, the voltage V is rising and the

current I is falling. In a period T3 (period of 9 seconds)

that follows the period T2, the clutch 20 is in an engaged

state. At the beginning of the period T3, the voltage V

drops (A part) and the current I rises sharply (B part).

It is considered that this is because the load increased

suddenly due to the clutch 20 being engaged. Thereafter,

the current I falls and eventually stabilizes (C part).

[0040] In Fig. 12 that relates to the Example, although

the waveforms of the current and voltage in the period Ti

and the period T2 are the same as in Fig. 11 relating to

the Comparative Example, the waveforms in the period T3

differ significantly between Fig. 11 and Fig. 12. In Fig.

12, the current value falls to the vicinity of zero at the beginning of the period T3 (D part). This is because energization stopping control was executed, and energization of the electric motor 5 was stopped. It is surmised that the reason the current value did not become completely zero was because of energization of the sensors and the characteristics of the three-phase motor. The energization stop time was set to 0.5 seconds, and upon 0.5 seconds elapsing from the time that energization of the electric motor 5 was stopped, the electric motor 5 restarted and simultaneously the cutting blade 9 also rotated. After restarting, the current rises as a whole (E part), and thereafter falls (F part), and eventually stabilizes (G part).

[0041] Comparing Fig. 11 relating to the Comparative

Example and Fig. 12 relating to the Example, since the

abrupt increase in current in the period T3 in Fig. 11

relating to the Comparative Example is not observed in Fig.

12 relating to the Example, a reduction in electric power

consumption is expected in the Example in comparison to the

Comparative Example. In order to confirm the electric

power consumption reduction effect, the operating time from

when the battery was fully charged until the electric motor

stopped due to battery discharge was measured for each of

the Comparative Example and the Example. Similarly to the

above experiment, one cycle was set to 10 seconds, with an engaged state of the clutch 20 being set to 9 seconds, and a disengaged state of the clutch 20 being set to 1 second.

The results of the experiment are shown in Table 1 below.

[0042] [Table 1]

Number of Cycles Operating Time

Comparative Example 309 cycles 51 mins, 30 secs

Example 434 cycles 72 mins, 20 secs

[0043] According to the results shown in Table 1, while

the number of cycles in the Comparative Example was 309,

the number of cycles in the Example was 434, which showed

that the number of cycles in the Example increased by 40%

(the operating time increased by 40%) compared to the

Comparative Example, and thus the effect of reducing the

electric power consumption could be confirmed. According

to this result, it can be understood that an abrupt

increase in current at the moment at which the clutch 20 is

engaged is a major factor that increases the electric power

consumption. On the other hand, when the electric motor 5

is restarted as in the Example, even though a large load is

applied at the time of restarting, the electric power

consumption is reduced compared to the Comparative Example.

This is because an electric motor has a characteristic of

generating a large torque when starting, and it is

considered that restarting of the electric motor 5 is not a factor that greatly increases the electric power consumption.

[0044] Therefore, according to the present invention,

since an abrupt increase in the current at a moment at

which the clutch 20 is engaged can be eliminated and

electric power consumption can be reduced, operation for an

extended period can be enabled without making the battery a

large size.

[0045] Further, since the effect of reducing the

electric power consumption is obtained by suppressing an

abrupt increase in the current at a moment at which the

clutch 20 is engaged, the effect of reducing the electric

power consumption increases as the frequency of engaging

and disengaging the clutch 20 increases. In this regard,

since a walk-behind lawn mower as illustrated in Fig. 1 is

used in a narrow area, the frequency of engaging and

disengaging the clutch 20 is high, and hence electric power

consumption can be reduced more effectively.

[0046] Whilst an embodiment of the present invention has

been described above, the above embodiment is an example

and may be appropriately modified. For example, although

in the above embodiment the clutch lever 12 is used as

operation means for operating the clutch 20, as long as the

clutch 20 can be operated, the operation means is not

limited to a lever structure.

[0047] Furthermore, although in the above embodiment the

detection of release of a state in which the clutch 20 is

disengaged is detection that is based on a change in a

signal value that is output from the clutch operation

detection sensor 31 as a result of operation of the clutch

lever 12, it suffices that the release of a state in which

the clutch 20 is disengaged can be detected, and another

method may be adopted as the detection method.

[0048] In addition, although the energization stopping

control adopted in the above embodiment is control that

stops energization of the electric motor 5 when a state in

which the clutch 20 is disengaged is released, an

energization stopping period is not limited thereto, and it

suffices that energization is stopped at least at the

moment at which the clutch 20 is engaged.

[0049] In this specification, the terms "comprise",

"comprises", "comprising" or similar terms are intended to

mean a non-exclusive inclusion, such that a system, method

or apparatus that comprises a list of elements does not

include those elements solely, but may well include other

elements not listed

[0050] The reference to any prior art in this

specification is not, and should not be taken as, an

acknowledgement or any form of suggestion that the prior

art forms part of the common general knowledge.

Reference Signs List

[0051] 1 electric work machine with cutting blade

3 front wheel

4 rear wheel

5 electric motor

9 cutting blade

12 clutch lever (operation means for clutch)

18 operation button

20 clutch

22 drive disk

28 friction plate

30 controller

31 clutch operation sensor

Claims

What is claimed is:

1. An electric work machine with cutting blade,

comprising:

a cutting blade;

an electric motor that rotationally drives the cutting

blade;

a clutch that engages and disengages motive power between

the electric motor and the cutting blade;

operation means for operating the clutch; and

controller for controlling operation of the electric

motor,

wherein:

by means of the operation means, it is possible to

switch between a state in which the clutch is disengaged

and motive power of the electric motor is not transmitted

to the cutting blade and a state in which the clutch is

engaged and motive power of the electric motor is

transmitted to the cutting blade, and

by stopping energization of the electric motor after a

state in which the clutch is disengaged is released, and

restarting the electric motor after a prescribed time

period elapses after stopping the energization, the

controller stops rotation of the electric motor during a

period that includes a moment at which the clutch is

engaged.

2. The electric work machine with a cutting blade

according to claim 1, wherein:

the controller recognizes release of a state in which

the clutch is disengaged, based on a signal from a sensor

that detects movement of the operation means.